In order to treat cancer, patients are usually exposed to radiation such as gamma rays or charged particles (for example, alpha particles). Beams of radiation are targeted so that the beam does not damage healthy tissue surrounding the cancerous tissue. It is necessary for hospitals to know the dosage, or level, of radiation that the user has been exposed to both at the site of the cancer and in surrounding areas. There is a need to record the level of radiation exposure, and to keep that data secure. Particularly in developing countries, where local treatment centres may only have limited resources, it is typical for the level of radiation exposure to be recorded locally and then transported to a central facility for analysis. Sometimes weeks can pass between recording of data and reading of data, and in that time data resolution (or accuracy) can decrease. It is therefore necessary to provide a means for storing data relating to level of radiation over a long period, particularly in high temperature environments.
Radiation dosimeter systems are also required for the measurement of the levels of radiation exposure, particularly in humans for the purpose of safety monitoring in environments where there is a risk to health from exposure to higher than recommended doses of radiation, for example, in nuclear power stations and nuclear-powered ships and submarines. Another important application of dosimeter systems is for monitoring radiation dose provided for sterilisation of objects, particularly food products, to ensure that a sufficient radiation dose is provided to kill microorganisms or biological pathogens which may be present on the objects.
Prior art devices for measuring radiation dosage include using Lithium Fluoride thermo-luminescent dosimeters (TLDs). However, these dosimeters are hydroscopic and so cannot be exposed to moisture. This is particularly difficult when working inside the human body. Furthermore, LiF dosimeters are commonly designed for dosages of less than 10 gray (Gy) as above 10 Gy the reading becomes non-linear. In the UK, radiotherapy treatment exposes users to doses in excess of 70 Gy (typically 20 Gy in one fraction of a treatment), so LiF dosimeters do not have enough fidelity, or resolution. Dosimeters have been developed for medical use which comprise disk-shaped radiation detectors. For in-vivo use, the disk-shaped detectors can be inserted into catheter tubes and placed in the body during radiotherapy treatment. The disks then have to be individually removed and placed into a cassette for reading in a machine. However, removing the disks and loading them into the cassette is a time-consuming and laborious process since the disks are difficult to manipulate, and consequently the overall procedure is slow and expensive.
Aspects of the present invention aim to address one or more drawbacks inherent in prior art methods and apparatus for measuring levels of radiation exposure, particularly in humans.